The key components of the complex pulmonary surfactant (PS) mixture include neutral, zwitterionic, and anionic lipids, as well as cationic proteins. Functional PS must adsorb within seconds at a newly formed air/water interface and stabilize the lungs mechanically during the breathing process. Lack of an adequate supply of PS in the alveoli can lead to Respiratory Distress Syndrome in premature infants or Acute Respiratory Distress Syndrome in adults. Treatment via surfactant replacement therapies is expensive. The fundamental mechanisms detailing how PS works are not yet well understood. Electrostatic interactions are thought to play a role in the initial adsorption process. The first aim of this proposal is to test the hypothesis that the effective screening of PS charge facilitates the close approach of the surfactant to the air/water interface, thereby enhancing the rate of adsorption. The second aim is to test whether the presence of protein enhances the adsorption rate by acting as an electrostatic tether or bridge between its own cationic charge and the anionic charge of the PL. These hypotheses will be experimentally tested with surface tensiometry and microscopy using a variety of surfactant and subphase compositions. Successful completion of this project should significantly contribute to the fundamental understanding of the PS adsorption mechanism.